Busted rim?

Danger_Uni: The groove is common on bike rims to show the level of sidewall wear due to brakes. I did not ask for it but the manufacturer put it in anyway. If you have a rim that broke along the groove, you can return it for warranty replacement.

All rims sold after April 2005 had no groove. Also the material was upgraded from 7005 T6 aluminum to stronger 7005H T6.

Kris

Also:

As a side note: I killed two of them on my KH20 05, since then the new rim without the groove has served me perfectly.